krb5_free_string takes a krb5_context

krb5_free_string takes a krb5_context

Give krb5_free_string a krb5_context, not just the string to free.

Reviewed-on: http://gerrit.openafs.org/3262
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 354d21878ed401c644a5392f86af3fe6e660801f)

Change-Id: Ief39cbd5edc9bd9298e199f974d3dcecef31a3d5
Reviewed-on: http://gerrit.openafs.org/4009
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>